This application claims the priority benefit of Taiwan application serial no.91206362, filed on May 7, 2002.
1. Field of Invention
The present invention relates to a non-volatile memory device. More particularly, the present invention relates to a back up power embodied non-volatile memory device.
2. Description of Related Art
Due to the popularization of electronic products, digital data is now routinely stored in memory devices for subsequent recall. To increase portability and facilitate easy access to stored digital data, detachable hard disks or optical disks have been used in the past. However, these conventional devices have several drawbacks. For example, a hard drive or an optical disk may store a large volume of data, however the intricate internal structure inside the hard drive is vulnerable to shock and impact. Although an optical disk is less vulnerable to impact, each optical disk has a fixed memory capacity and requires special read-out equipment such as a re-writable optical device to access and re-write data. In other words, both detachable hard drives and optical disks are easy to use but inconvenient to carry.
To increase portability of storage devices and limit the need for special devices, manufacturers have developed non-volatile memory devices such as flash memory. These non-volatile memory devices may connect with a host system through various types of external bus interfaces including, for example, the universal serial bus (USB) interface, RS232 interface and the 1394 interface. The non-volatile memory device not only carries out data transfer with the host system via the external bus, but also obtains power from the host system via the external bus as well. Portability and ease of connection with various host systems are the major reasons for the popularity of non-volatile memory devices. However, the non-volatile memory device must engage with the external bus of a host system to access and transfer data. Hence, any untimely unplugging of the device from the external bus may corrupt the data inside a file. If the memory device is unplugged during a file allocation table (FAT) refreshing operation, an incomplete FAT file is created due to the sudden power outage.
In brief, untimely unplugging of externally connected non-volatile memory devices may lead to possible deletion of transfer data or so damage the links in a FAT file that important data is forever lost.
Accordingly, one object of the present invention is to provide a back up power embodied non-volatile memory device. The device contains a back up internal power source that automatically cuts in when external power to the device suddenly terminates. The back up internal power source provides necessary power to download data already transferred to the memory into appropriate files and execute other necessary programs to render the file readable. In addition, if power to the non-volatile memory device is accidentally cut when a file allocation table (FAT) is being refreshed, the back up power also provides the necessary power for completing the refresh operation.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a back up power embodied non-volatile memory device. The memory device includes a connection port, a power supply unit and a memory system. Host data and host power are provided to the non-volatile memory device through an external bus of the connection port. The memory system temporarily holds the data picked up by the connection port and subsequently transfers the data to the non-volatile memory. The power supply unit provides back up power to the memory system when power from the host system is cut. Hence, the temporarily stored data inside the memory system is ultimately transferred to the non-volatile memory to become readable data.
This invention also provides an alternative back up power embodied non-volatile memory device. The memory device includes a connection port, a buffer unit, a non-volatile memory, a battery and a memory controller. The connection port is connected to a host system. The host system provides host data and host power to the back up power embodied non-volatile memory device through the external bus on the connection port. The buffer unit temporarily holds data received by the connection port. The memory controller controls the writing of data from the buffer unit into the non-volatile memory and monitors the presence of host power. When host power is cut out in the middle of a data transfer operation, the battery provides back up power to complete the write, operation.
The connection port is an interface connection device suitable for interfacing with any one of the following interfaces, including the universal serial bus (USB) interface, the 1394 interface, the RS232 interface, the parallel transmission interface, the PCMCIA interface, the CF interface, the SD interface, the MMC interface and the memory stick interface.
The back up power embodied non-volatile memory device according to this invention is capable of detecting any change in the power provided by the host system. If host system power suddenly fails before the completion of a data transfer operation, internal back up power immediately cuts in to complete the writing of transmitted data into the non-volatile memory. Hence, the invention guarantees the writing of all received data into the non-volatile memory so that none of the data transmitted to the non-volatile memory device is lost.
In addition, the back up power within the non-volatile memory device also provides necessary power to complete any FAT refreshing operation if host power is cut prematurely. Hence, integrity of the stored data can be maintained.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.